In one line
The subject a creator makes content about, and the community that follows it.
A Bengaluru creator posts mostly about home workouts: fitness is their niche. On Influcius, creators choose from 24 niches, from Food & drink to Devotional.
Audience size says nothing about expertise: a small creator in the right niche can explain a product better than a big one outside it.
Agree: match the niche to what the product claims and who it serves.